Brushes used in commutating electric machines such as motors and generators tend to create sparks which wear down the brushes and commutator contacts. Such sparks are undesirable because they reduce both the life of the brushes and commutator, and the performance of the machine.
U.S. Pat. No. 3,980,914 describes a solid brush for electric machines which has carbon fibers attached to the leading and trailing edges of the brush, to reduce sparking. However, that brush is several times more expensive than ordinary solid brushes. Thus, there is a need for brushes for commutating electric machines which reduce sparking and also are relatively inexpensive.
Accordingly, one object of this invention is to provide new and improved carbon brushes for commutating electric machines.
Another object is to provide new and improved carbon brushes which prevent or reduce sparking.
Still another object is to provide new and improved carbon brushes which prevent or reduce sparking and are relatively inexpensive.